He might be having issue updating the original RC Pro not RC Pro 2. Not sure what version is RC Pro 2 but the FW he is on was my previous FW on RC Pro.
My RC Pro is 03.02.0900. Maybe try clearing cache first and do the update through Profile rather than Camera View in FlyApp. Make sure the controller is fully charged. If this won't help, I'd reset the RC Pro and start from scratch.
Ok, back to my question. Do you by any chance might know why this actually is the case? Could that have something to do with the use of the dual gain to enhance dynamic range when shooting in D-Log M as discussed in the M4P forum? Maybe this...